Communication systems are endemic in modern society. Communication of data pursuant to many varied types of communication services is regularly needed. A communication system is used by which to effectuate the communication of the data. Due to advancements in communication technologies, new types of communication systems are being developed.
A communication system includes at least a first communication station and a second communication station interconnected by way of a communication channel. Data is communicated by the first communication station, referred to as a sending station, to the second communication station, referred to as a receiving station, by way of the communication channel. Data that is to be communicated by the sending station is converted, if needed, into a form to permit the data to be communicated upon the communication channel. And, the receiving station detects the data communicated upon the communication channel and recovers the informational content thereof.
A radio communication system is a type of communication system. In a radio communication system, a radio channel, defined upon a radio air interface, forms the communication channel interconnecting the sending and receiving stations. Conventional wireline communication systems, in contrast, require the use of fixed, wireline connections extending between the communications stations upon which to define the communication channel.
A radio communication system provides various advantages in contrast to a wireline counterpart. Initial installation and deployment costs associated with a radio communication system are generally less than the costs required to install and deploy a corresponding wireline communication system. And, a radio communication system can be implemented as a mobile communication system in which one or more of the communication stations operable therein is permitted mobility.
A cellular communication system is an exemplary type of mobile radio communication system. Cellular communication systems have been installed throughout significant portion of the populated areas of the world and have achieved wide levels of usage. A cellular radio communication system is a multi-user communication system in which radio communications are provided with a plurality of mobile stations. Telephonic communication of voice and data is effectuable by way of the mobile stations. Mobile stations are sometimes of sizes to permit their convenient carriage by users of the mobile stations.
A cellular radio communication system includes network infrastructure, that is installed throughout the geographical area that is encompassed by the communication system. Mobile stations operable in the cellular communication system communicate, by way of radio channels, with base stations that form parts of the network infrastructure of the communication system.
Base stations are fixed-site radio transceiver that transceive data with the mobile stations. The base stations are installed at spaced-apart locations throughout the geographical area encompassed by the communication system. Each of the base stations defines a cell, formed of a portion of the geographical area. A cellular communication system is so-called because of the cells that together define the coverage area of the communication system.
When a mobile station is positioned within a cell defined by a base station, communications are generally effectuable with the base station that defines the cell. Due to the inherit mobility of a mobile station, the mobile station might travel between cells defined by different ones of the base stations. Continued communications with the mobile station is provided through communication hand off procedures between successive ones of the base stations defining the successive ones of the cells through which the mobile station passes. Through appropriate positioning of the base stations, the mobile station, wherever positioned within the area encompassed by the communication system, shall be within communication proximity of at least one base station.
Only relatively low-powered signals need to be generated to effectuate communications between a mobile station and a base station when the base stations are suitably positioned at selected spaced-apart locations. Hand-offs of communications between the successive base stations permit continued communications without necessitating increases in the power levels at which the communication signals are transmitted. And, because the signals that are generated are all generally of low powered levels, the same radio channels are able to be reused at different locations of the cellular communication system. The frequency spectrum allocated to a cellular communication system is thereby efficiently utilized.
A cellular communication system is constructed, generally, to be operable pursuant to an operating specification of a particular communication standard. Successive generations of communication standards have been developed, and operating specifications defining their operational parameters have been promulgated. First-generation and second-generation cellular communication systems have been deployed and have achieved significant levels of usage. Third-generation and successor-generation systems are undergoing development, standardization, and, at least with respect to the third-generation systems, partial deployment.
An exemplary third-generation cellular communication system is a system that operates pursuant to the operating protocol set forth in a CDMA 2000 operating specification. A CDMA 2000 cellular communication system, constructed in conformity with the CDMA 2000 operating specification, provides for packet-based data communication services.
Various technology proposals by which to effectuate communication of packet data at high data rates in a CDMA 2000 communication system have been proposed. By transmitting data at high data rates, increased amounts of data are able to be communicated in a given time period.
The 1xEV-DV data communication service is one such proposal. And, the 1xEV-DO data communication service is another such proposal. These data communication services provide for the communication of data at any of several selected data rates. And, systems providing for such communication services are sometimes referred to as being multi rate communication systems. Other communication systems that permit data to be communicated at any of two or more different data rates are also sometimes referred to as being multi rate, or multiple, data rate systems.
In the CDMA 2000 system that provides for multiple data rate communication services, data that is to be communicated is communicated at selected data rates on reverse links. That is to say, data that is communicated by a mobile station to a network portion of the communication system is communicated, upon a reverse link channel at a selected data rate. A Pilot signal is also communicated by the mobile station to the network infrastructure along with the communication of the data. The pilot signal is communicated upon a reverse pilot channel, and the data is communicated upon a data channel. The pilot signal is used at the network infrastructure to assist in coherent demodulation of the data communicated upon the data channel.
In conventional CDMA 2000 systems, i.e., CDMA communication systems that do not provide for high data rate communications at multiple data rates that are quickly changeable, the pilot signal is of a constant, or slowly changing, signal-to-noise ratio (SNR) level (e.g., received pilot signal to noise ratio). However, when employed in a system that provides for multiple data rate communications, such as 1xEV-DV communication services, fast scheduling and rate control impact the power control operation of the communication system. Conventionally, the SNR level of the pilot signal must be set at a high SNR level to ensure successful communication of the data at a highest data rate of the multiple data rates. In the event that data is communicated at a data rate that is lower than the highest data rate, the pilot signal is of a SNR level that is greater than that which is needed. The pilot signal, during such times, therefore, is of an excessive power level. Communication performance in the communication system is adversely affected. And, when the mobile station is powered by a battery power supply, the battery power supply is depleted of stored energy at a rate greater than that which is required.
If a better manner could be provided by which better to match the power level of the pilot signal with the data rate at which the data associated therewith is communicated, improved system performance would be possible.
It is in light of this background information related to radio communication systems capable of communicating data at multiple data rates that the significant improvements of the present invention have evolved.